Photobiological experiments are planned next year using EPR spectroscopy and nitroxide paramagnetic probes to investigate events following blue light photoreception in plant cells: Arabidopsis thaliana and Lemna anisulca. We teste d the applicability of existing EPR equipment to the planned studies. It was concluded that irradiation of plant material with high-intensity light during the EPR spectra measurement will require construction of a special resonator for L-band.